I hate to hear things rattling around in the refrigerator. We started out trying to solve the problem with some spring-loaded bars from Camping World but they didn't work very well. We then found some plastic storage trays which fit the shelves. That made it easy to store things but they interrupted the air flow in the refrigerator which wasn't good.
After replacing the original refrigerator with an Isotherm unit, we finally found some wire trays which solved the air flow problem. However, they were slightly narrower than the inside width of the refrigerator and therefore slide sideways unless they were completely full. That problem was finally solved with pieces of foam pipe insulation from the hardware store. The overall diameter of the insulation was slightly wider than the space between the trays...slicing the insulation lengthwise resulted in a nice tight fit:
No more rattles!